The present invention relates to an apparatus and, in particular to an electrical switch apparatus, capable of providing an operator with a tactile sensation.
A conventional switch apparatus includes a push button, a snap dome connected to the push button, and an electrical contact on a mounting surface. When a minimal amount of force is applied to the push button by an operator, the snap dome resists movement of the push button.
As more force is applied to the push button by the operator, movement of the push button is effected, but the movement is still resisted by the snap dome. When the force applied to the push button increases to a predetermined amount, the snap dome snaps inwardly and no longer resists movement of the push button. When the snap dome snaps inwardly the operator feels a distinct tactile sensation. Also, a contact surface on the snap dome engages the electrical contact on the mounting surface and completes a circuit for performing a function.
The conventional apparatus may require a relatively small force by the operator (due to a relatively thin snap dome) to complete the circuit and may have a relatively long cycle life. Alternatively, the apparatus may require a relatively large force by the operator (due to a relatively thick snap dome) to complete the circuit, but may then have a relatively short cycle life because of greater stress incurred by the relatively thick snap dome with each cycle of operation.
The apparatus of the present invention includes a depressible member, a first membrane, and a second membrane. The depressible member has an unactuated condition and an actuated condition. The depressible member is moved by an operator. The first membrane is connected with the depressible member. The first membrane resists movement of the depressible member from the unactuated condition to the actuated condition. The first membrane further provides an increasing return force urging the depressible member to the unactuated condition as the operator moves the depressible member from the unactuated condition to the actuated condition. The second membrane also resists movement of the depressible member to the actuated condition. The second membrane further provides an increasing return force to the depressible member as the operator moves the depressible member to the actuated condition. The first membrane initially acts alone and then acts simultaneously with the second membrane. The first and second membranes provide a tactile sensation to the operator due to a reduction in the combined return forces applied to the depressible member by the first and second membranes during a portion of the movement of the depressible member by the operator.
The first and second membranes may be relatively thin and thus have a relatively long cycle life. Also, since the first and second membranes act simultaneously, the operator experiences a relatively high resistance to movement of the depressible member and a distinct tactile sensation when the reduction in the combined return forces occurs.